Modernize Nomad driver for Singularity/Apptainer: dynamic binary detection, new container flags, bug fixes

[Copilot]

Modernizes the nomad-driver-singularity task driver to work with current Go versions, adds Apptainer support, fixes several bugs, and exposes missing Singularity/Apptainer CLI flags.

Dependency Updates

• hashicorp/nomad bumped from v0.9.0-rc2 → v0.12.12 — fixes a runtime panic caused by the old ugorji/go codec using a duplicate-character base64 alphabet rejected by Go 1.22+
• hashicorp/go-hclog updated to latest
• github.com/sylabs/singularity removed — was only used to supply the hardcoded version string "3.1.1"
• go 1.21 language directive added to go.mod

Apptainer Support + Dynamic Binary/Version Detection

• Removed the hardcoded /usr/local/bin/singularity constant
• New findBinary(configured string) helper: returns the configured path if set, otherwise searches $PATH for singularity then apptainer
• New getVersion(binPath string) helper: runs <bin> version and returns the live output instead of the static string "3.1.1"
• New driver config option singularity_path so operators can point directly at /usr/bin/apptainer
• Removed the init() function in main.go that called useragent.InitValue("singularity", "3.1.1")

plugin "nomad-driver-singularity" {
  config {
    enabled          = true
    singularity_path = "/usr/bin/apptainer"
  }
}

New Task Config Flags

HCL key	Singularity/Apptainer flag
containall	--containall
writable_tmpfs	--writable-tmpfs
net	--net
hostname	--hostname

Bug Fixes

• Duplicate SetDriverState call in StartTask — the second identical call was removed
• timeout * time.Second in shutdown() — timeout is already a time.Duration; multiplying it by time.Second was producing vastly inflated timeouts
• Missing NoCgroups bool in the Config struct — no_cgroups was declared in configSpec but never decoded into the struct
• ioutil.Discard replaced with io.Discard

Other Changes

• examples/example.hcl: added the MPL 2.0 license header
• README.md: updated requirements (Nomad v0.12+, Go v1.21+, Apptainer v1.0+ as alternative), added full driver config and task config reference tables with Apptainer usage example, and added step-by-step testing instructions for running the driver on a Nomad client node
• Tests: added TestFindBinary and TestPrepareContainer (9 sub-tests covering all new flags)
• gofmt applied to all changed Go files

Testing

• ✅ go build ./... passes
• ✅ go vet ./... passes
• ✅ All 11 tests pass (go test ./...)
• ✅ CodeQL security scan: 0 alerts
• ✅ gofmt formatting applied

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[abhi18av]

@copilot summarize all changes

[Copilot]

@copilot summarize all changes

Here's a summary of all changes made across the two commits:

---

Dependencies (go.mod / go.sum)

• hashicorp/nomad bumped from v0.9.0-rc2 → v0.12.12 — fixes a runtime panic caused by the old ugorji/go codec using a duplicate-character base64 alphabet that Go 1.22+ rejects
• hashicorp/go-hclog updated to latest
• github.com/sylabs/singularity removed — was only used to supply the hardcoded version string "3.1.1"
• go 1.21 language directive added to go.mod

---

Apptainer support + dynamic binary/version detection (driver.go, singularity.go, main.go)

• Removed the hardcoded /usr/local/bin/singularity constant
• New findBinary(configured string) helper: returns the configured path if set, otherwise searches $PATH for singularity then apptainer
• New getVersion(binPath string) helper: runs <bin> version and returns the live output instead of the static string "3.1.1"
• New driver config option singularity_path so operators can point directly at /usr/bin/apptainer
• Removed the init() function in main.go that called useragent.InitValue("singularity", "3.1.1")

---

New task config flags (driver.go, prepare.go)

HCL key	Singularity/Apptainer flag	Addresses issue
containall	--containall	hpcng#35
writable_tmpfs	--writable-tmpfs	hpcng#36
net	--net	hpcng#33
hostname	--hostname	hpcng#28

---

Bug fixes (driver.go, handle.go, prepare.go)

• Duplicate SetDriverState call in StartTask — the second identical call was removed
• timeout * time.Second in shutdown() — timeout is already a time.Duration; multiplying it by time.Second was incorrect (e.g. a 30s timeout became 30 × 10⁹ seconds)
• Missing NoCgroups bool in the Config struct — no_cgroups was declared in configSpec but never decoded into the struct
• ioutil.Discard replaced with io.Discard (standard library, not deprecated)

---

Other

• examples/example.hcl: added the MPL 2.0 license header (issue example.hcl: no license hpcng/nomad-driver-singularity#29)
• README.md: updated requirements (Nomad v0.12+, Go v1.21+, Apptainer v1.0+ as alternative), added full driver config and task config reference tables, Apptainer usage example
• Tests (driver_test.go): added TestFindBinary and TestPrepareContainer (9 sub-tests covering all new flags)
• gofmt applied to all changed Go files

[abhi18av]

@copilot create testing instructions, assuming a nomad client running on a compute node with proper singularity/apptainer setup.

[Copilot]

@copilot create testing instructions, assuming a nomad client running on a compute node with proper singularity/apptainer setup.

Added a "Testing on a Nomad client node" section to README with step-by-step instructions for validating the driver on a compute node (build/install, config, runtime check, smoke-test job, and log inspection). Commit: 95ce0ba.